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Description/Abstract

Traditionally, engineers have used bearings and expansion joints to accommodate bridgeexpansion and contraction caused by daily and seasonal temperature fluctuations. Studies carriedout in the late 1980s showed durability problems can be associated with bearings and expansionjoints [Wallbank, 1989]. Since the mid twentieth century Integral Bridges with no expansionjoints or bearings have been used. Deck expansion and contraction is accommodated bymovement of the abutments into the retained fill. This eliminates the problem of durability butthe movement of the abutments has been thought to cause a build up of horizontal pressures,particularly in the case of full height abutments. In the United Kingdom BA42/96 [HighwaysAgency, 2000] was issued and gave guidance on the soil pressures that should be adopted indesign. The validity of the work on which the code of practice was based is a subject ofcontinued debate by both researchers and practicing engineers. For this reason Integral Bridgeshave been used much less widely than conventional bridges.As part of a strategy by the University of Southampton to further investigate the occuring soilpressures, Xu [2005] carried out radial controlled triaxial tests of granular material under cyclicloading. The applied strain and stress path used represented that typically experienced by anelement of retained material behind an integral bridge abutment. This was the first time that thefundamental behaviour had been investigated in this way.The further research discussed in this paper builds upon this by use of numerical modelling.The fundamental behaviour of granular material under this particular loading could not berepresented by any available constitutive model and therefore a new model was be developedbased on this behaviour. The basis of the model and initial validation process are discussed. Thefirst stage of the validation process was implementation in a commercially available spreadsheetpackage. This was then used to develop a model in the Finite Difference Method package FLAC.Once this was implemented, the triaxial tests were modelled and the results compared toexperimental data